Pharmaceutical products for use in the treatment of hyperphosphatemia are known in the art. These include those disclosed in U.S. Pat. No. 7,588,782, which describes certain lanthanide containing compounds including lanthanum dioxycarbonate (also referred to herein as LDOC) as well as U.S. Pat. Nos. 5,968,976; 7,381,428; and 7,465,465, describing various lanthanum carbonate hydrates including those of the formula La2(CO3)3.xH2O (also referred to herein as lanthanum tricarbonate). These compounds work by binding phosphate that a subject consumes. One such compound is marketed under the trademark FOSRENOL. Other products for treatment of hyperphosphatemia include RENAGEL, which is a polymeric phosphate binder also known as sevelamer HCl.
In particular, U.S. Pat. No. 7,588,782 describes the production of, inter alia, lanthanum dioxycarbonate from a reaction of lanthanum chloride with sodium carbonate to produce what is referred to therein as a lanthanum oxycarbonate (La2O(CO3)2.xH2O). This is then heated in a furnace at high temperatures to produce lanthanum dioxycarbonate. See generally the '782 patent, example 5. It has subsequently been learned that one compound characterized in the '782 patent as lanthanum oxycarbonate is in fact a lanthanum carbonate hydroxide (LaCO3OH or LCH) with or without further associated water. It is this compound which is heated to produce lanthanum oxycarbonate. The LDOC material finally produced is said to be crystalline in nature, made up of approximately round particles of about 100 nanometers in size and is noted as being anhydrous. FIG. 20 of the '782 patent shows improved phosphate binding kinetics for LDOC made in accordance with example 5 when compared to various hydrates of lanthanum tricarbonate. Specifically, at 10 minutes, lanthanum dioxycarbonate had bound somewhere between about 70 and 80 percent of the available phosphate where lanthanum tricarbonate tetrahydrate had bound only about 40 percent. This test was undertaken at pH 3.
It was discovered, however, the phosphate binding kinetics of lanthanum dioxycarbonate as described in the '782 patent was not consistent at all pHs. As pH tended to increase, as would happen in the digestive tract of a mammal, the binding kinetics slowed. The '782 patent describes a material of great value pharmacologically and great utility. But, as with most things, there is room for further development.